In cold climates it is often necessary to dig into frozen ground, for example to service underground utilities. Frozen ground is extremely difficult to dig, because the moisture content of the soil acts as a cement producing a solid mass somewhat akin to concrete with the soil acting as an aggregate. Devices have therefore been proposed for thawing frozen ground to allow the desired ground digging. The prior art devices for this purpose have included open bottomed housings containing heaters that generate a hot zone above the ground, under the housing. With such a device, the accumulation of steam within the housing acts to inhibit the evaporation of liquid water on the ground, which acts as a heat absorbing, insulating layer in the top layer of the ground, so that heat penetration into the soil is very slow.
Other disadvantages of the known devices include the use of refractory lined combustion chambers that increase weight and reduce the available area for heating and ineffecient systems for using hot gases for thawing.
The present invention is concerned with an improved ground thawing device of this type.